Process of gelling tmetn nitrocellulose explosives using nitroparaffin solvents and tmetn nitrocellulose explosive gels



United States Patent PROCESS OF GELLING TMETN NITROCELLULOSE EXPLOSIVES USING NITROPARAFFIN SOL- VENTS AND TMETN NITROCELLULOSE EXPLO- SIVE GELS George L. Griflith, Coopersburg, and William J. Carroll, Jr., and William L. Sclrwoyer, Allentown, Pa., assignors to Commercial Solvents Corporation, Terre Haute, Ind., a corporation of Maryland No Drawing. Filed Jan. 8, 1968, Ser. No. 696,125

Int. Cl. C(lfib 5/02, 21/00 US. Cl. 149-20 28 Claims ABSTRACT OF THE DISCLOSURE 'A process is provided for preparing polyolpolynitratenitrocellulose explosive gels, by dissolving the polyolpolynitrate, nitrocellulose, and any other components in a nitroparaffin solvent, and then volatilizing the solvent, to form the gel.

Polyolpolynitrate-nitrocellulose explosive gels also are provided, which can be formulated to any desired hardness and sensitivity and which can also be in any physical form, including particulate and sheet form.

Trimethylolethane trinitrate-nitrocellulose explosive gels in particular are made possible for the first time.

This invention relates to a process for preparing gelled explosives based on a polyol polynitrate such as trimethylolethane trinitrate and nitrocellulose, employing a nitroparalfin solvent to form the gel, and to explosive gels based on a polyol polynitrate such as trimethyolethane trinitrate and nitrocellulose, and more particular- 13 to a process for preparing gelled explosives containing a polyol polynitrate and nitrocellulose, forming a solution thereof in a nitroparaflin solvent and thereafter removing the nitroparaffin solvent to form the gel; and to explosive gels comprising a polyol polynitrate and, nitrocellulose.

Blasting gelatins and gelatin dynamites, based on nitroglycerine and introcellulose, of which gelignite is an example, have been known and widely used for many years. These dynamites commonly contain additional explosive sensitizers, such as inorganic salts, for example, ammonium nitrate, combustible materials such as fuels, and other conventional explosive ingredients. Permissible explosives and smokeless powders may also incorporate suchgels.

Trinitroglycerine and dinitroglycerine are good solvents for nitrocellulose, and such gels are readily formed by dissolution of the nitrocellulose therein, employing the appropriate proportion of nitroglycerine to dissolve the nitrocellulose to form a gel of the desired consistency. Polynitroaromatic compounds also are solvents or gelatinizing agents for nitrocellulose. However, liquid polyol polynitrates that are not good solvents for nitrocellulose cannot form gels in this manner, inasmuch as the nitrocellulose is not dissolved or softened by the polyol polynitrate. Thus, for example, it is quite impossible to prepare gelled explosives based on trim-ethylolethane trinitrate and nitrocellulose, because trimethylolethane trinitrate has virtually no solvent power for nitrocellulose. The same deficiency is found with other higher molecular weight aliphatic polyol polynitrates, usually those having a ratio of carbon atoms explosive composition that is ob- ICC tained from mixing these components is a particulate material, with the trimethylolethane trinitrate absorbed on the nitrocellulose, if the proportion of trimethylethane trinitrate is low, or if a sufiicient proportion of trimethlolethane trinitrate is used, in excess of that which can be absorbed on the nitrocellulose, the composition is a thick slurry. Such compositions are not satisfactory, and are not competitive with the true gels, because the composition is diflicult to employ, and. because the sensitivity and instability of nitrocellulose makes the composition dangerous to handle.

In accordance with the invention, it has been determined that it is possible to form explosive gels based on nitrocellulose and a polyol polynitrate, such as trimethylolethane trinitrate, that has substantially no solvent power for nitrocellulose, if these explosive ingredients are combined with a volatile nitroparaflin solvent in a sufiicient amount to dissolve the nitrocellulose and the polyol polynitrate. The solvent is then removed from the resulting composition, and as this is done, the solution thickens and a gel of the polyol polynitrate and nitrocellulose is obtained eventually. Such gelled compositions can be formulated with additional explosive ingredients, such as explosive sensitizers, for instance, inorganic nitrates and other inorganic oxidizers, other sensitizing explosives, and fuels, and can be brought to any desired consistency or physical condition.

The process of the invention is applicable to any polyol polynitrate that is soluble in the nitroparatfin solvent, and that has no solvent power for nitrocellulose. Such polyol polynitrates are aliphatic in structure, and have from two to six carbon atoms, and not more than one nitro group for each 1.5 carbon atoms of the polyol, and from two up to a total of about five nit-r0 groups per molecule. Typical polyol polynitrates of this class include trimethylolethane trinitrate (which is preferred), dipropylene glycol dinitrate and dimethylolethane dinitrate.

Any type of nitrocellulose can be employed. A fully nitrated trinitrocellulose has the, highest nitrogen content (14.14% N), but the commercially available trinitrocelluloses having from 13.5 to 14% nitrogen are quite satisfactory. Any nitrocellulose having from 0.5 to

3 nitro groups per anhydroglucose unit of the cellulose can be employed, with excellent results. The preferred nitrocelluloses have from about 8% to about 14.14% nitrogen.

The amount of nitrocellulose can be varied over a wide proportion, according to the sensitivity and consistency desired.

The nitroparafiin employed has no effect on the con:

sistency ofthe final gel, but the relative proportions of polyol polynitrate and nitrocellulose do. Inasmuch as the polyol polynitrate is a liquid, and the nitrocellulose is a solid, the larger the proportion of polyol polynitrate, the greater the tendency of the final gel to be a thick semifiuid thixotropic or soft gel. Very hard gels can be obtained employing a large proportion of nitrocellulose. In general, the proportions of polyol polynitrate and nitrocellulose required for a gel of given hardness are best determined by trial and error, because the hardness of the gel depends to a considerable extent upon the particular polyol polynitrate employed, and the nitrogen content of the nitrocellulose.

Satisfactory hard explosive gels are obtained, of high sensitivity and adequate explosive power, when the composition contains from about to about 60 parts of nitrocellulose, and from about 40 to about 90 parts of polyol polynitrate. Soft gels are obtained when the nitrocellulose proportion is from 0.2 to 10 parts and polyol polynitrate from 99.8 to 90 parts. Thus, the proportion of polyol polynitrate can be varied to a considerable extent and a proportion within the range from about 40 to about 99.8 parts of polyol polynitrate to from about 0.2 part to about 60 parts of nitrocellulose can be used.

The higher the proportion of nitrocellulose, the higher the sensitivity and explosive power of the composition. The polyol polynitrate has a desensitizing effect. In general, the upper limit on the amount of polyol polynitrate 'will depend'upon the explosive power and sensitivity that is desired, and the lower proportion will depend upon the degree of desensitization of the nitrocellulose that is required for the end use of the composition.

The nitroparafiin that is employed should be sufficiently volatile at atmospheric temperatures, or at a temperature below about 60 C., under vacuum, if necessary, so that it can be removed virtually quantitatively from the composition after the polyol polynitrate and nitrocellulose have been dissolved therein, so as to form the desired gel. Such nitroparafiins have from one to about six carbon atoms and one nitro group, and include nitromethane, nitroethane, l-nitropropane, Z-nitropropane, l-nitrobutane, and l-nitrohexane. These nitroparafiins have a boiling point below about 150 C., but higher boiling nitroparaifins can be used if they are removed under vacuum. They are not explosives, and cannot be exploded with detonating caps, differing in this respect from the polyol polynitrates. A furtherdistinction is their volatility despite their high boiling point. Nitromethane, for example, the lowest molecular weight compound of the series, has a boiling point of 101.2 C. and yet it is quantitatively volatilized from the solution on standing in the atmosphere for from eight hours to three days. The relatively high boiling point is important to the formation of a gel, because it means that the nitroparaffin is only slowly volatilized from the solutions employed as a starting material in the preparation of the gels of the invention. A slow volatilization of the nitroparaffin may facilitate the formation of the final explosive gel that is the desired product of the invention.

The amount of nitroparafiin solvent is not critical. A sufficient amount is employed to dissolve the nitrocellulose and polyol polynitrate that is present. Depending upon the solubility of the nitrocellulose and the polyol polynitrate, as little as 20% by weight of the composition can be employed. There is no upper limit, inasmuch as all of the nitroparaffin solvent will eventually be removed, but there is obviously no need to employ more than is necessary to dissolve the components, since any excess nitroparaffin must also be evaporated in forming the gel with a resultant increase in the time required to form the gel. Thus, the upper limit is normally not in excess of about 500% by weight of the composition.

The gelled explosive compositions in accordance with the invention are quite versatile, and find application in a Wide variety of explosive formulations, among them, blasting gelatins, gelatin dynamites, smokeless powders, permissible explosives, and nitrocarbonitrate explosives. Blasting gelatins are based on the polyol polynitrate-nitrocellulose gel, with no other components except possibly a solvent, such as acetone, ether-alcohol, or nitrobenzene.

Gelatin and semi-gelatin dynamites contain, in addition to the polyol polynitrate-nitrocellulose gel, an inorganic oxidizer and a combustible material. The following is a general formulation:

Percent by weight Polyol polynitrate 5 to 95 Nitrocellulose 0.1 to Inorganic oxidizer 5 to 95 Combustible material or fuel 0to 25 Gelatin dynamites usually employ a softer gel, and less nitrocellulose, than a blasting gelatin.

Blasting gelatins and gelatin dynamites can be packaged in block form by filling the solution of polyol polynitratenitrocellulose and any other components in the nitroparaffin solvent into containers of the desired size, and then allowing the solution to gel by removal of the solvent. This can be expedited by warming the containers in a vacuum oven. Then, after the gels have set, the containers are capped and sealed. Stick gelatin dynamites are easily prepared in this way.

Semi-gelatin dynamites can be prepared by first mixing the nitrocellulose, nitrop'araffin and polyol polynitrate, and then allowing the nitroparaffin to evaporate, forming a viscous liquid: The 'viscous liquid is then blended with the inorganic oxidizers, fuels, or sensitizers desired, forming a damp granular mixture. The mixture is then packaged in cartridges, using conventional dynamite pack machines.

Smokeless powders are in particulate form and are based on the polyol polynitrate-nitrocellulose gel as one component, in combination with the usual components to control the rate of burning. The types of smokeless powders that can be formulated usingthe gels of the invention include double base powders and ball-grain powders. Typical general formulations are as follows:

Double base powder: Percent by weight Polyol polynitrate 5 to 60 Nitrocellulose 5 to Inorganic oxidizer 0 to 50 Combustible material or fuel 0 to 5 Ball-grain powder:

Polyol polynitrate 5 to 60 Nitrocellulose 95 to 40 Inorganic oxidizer 0 to 20 Combustible material or fuel 0 to 15 Gelled pellets of smokeless powder can be prepared by stirring the solution composed of polyol polynitrate, nitroparaffin solvent, and nitrocellulose rapidly with hot water, heating the mixture at an elevated temperature in order to remove the nitroparaflin and set the gel particles, while at the same time dispersing the solution into small droplets so that the gel particles are formed in finely-divided dispersed form in the water. The particles can then be separated from the water by screening and drying. The resulting composition is a pelleted smokeless powder, the size of whose pellets depends upon the degree of dispersion and the mesh size of the screen through which the composition is passed.

In nitrocellulose-polyol polynitrate formulations, as the inorganic oxidizer there can be employed any inorganic oxidizer, such as an inorganic nitrate, inorganic chlorate, or inorganic perchlorate. Exemplary are ammonium nitrate, the alkali metal nitrates, for example, sodium nitrate and potassium nitrate, alkaline earth metal nitrates, such as calcium nitrate, barium nitrate, and strontium nitrate, ammonium chlorate, the alkali metal chlorates, such as sodium chlorate, and potassium chlorate, alkaline earth metal chlorates, such as calcium chlorate, strontium chlorate and barium chlorate, ammonium perchlorate, the alkali metal perchlorates, such as sodium perchlorate and potassium perchlorate, and the alkaline earth metal perchlorates, such as calcium, barium, and strontium perchlorates. Ammonium nitrate is the preferred oxidizer, because it is readily available, and has high explosive power. (Zombinations of ammonium nitrate and alkali metal nitrates, such as sodium nitrates and ammonium nitrate, with the alkali metal nitrate in a minor proportion, are also frequently preferred for many uses.

As the combustible material or fuel, any carbonaceous fuel can be employed, such as, for instance, powdered coal, coal dust, camphor, lampblack, charcoal, bagasse, dextrin, starch, wood meal, wood flour, bran, pecan meal or similar nut shell meals, vaseline, and paraffin oil. A carbonaceous fuel when present will usually comprise from about to about 30% of the composition.

Metal fuels also can be employed, alone or in combination with carbonaceous fuels. Illustrative particulate num, atomized aluminum, ferrophosphorus, and ferro- Tnum, atomized aluminum, ferrophosphorus, and ferrosilicon. A metal fuel when present will usually comprise about 0.5 to about 30% of the composition, preferably from 0.5 to 5%, in the case of aluminum.

Stabilizers such as diphenylamine, centralites, zinc oxide and calcium carbonate can also be present. Only small amounts, from 0.1 to 5 need be used.

The polyol polynitrate-nitrocellulose explosive gels of the invention can also be employed in deflagrating or detonating fuse. In this case, the solution of polyol polynitrate, nitrocellulose and nitroparaffin is run into the fuse enclosure or sheath, and allowed to set in situ by evaporation of the nitroparafiin. Such a fuse composition can incrude a fuel, and an inorganic oxidizer, so as to control the burning rate. As the inorganic oxidizer, any of the oxidizers referred to above can be employed. The proportion of polyol polynitrate, nitrocellulose, oxidizer, and fuel will normally be within from about 5 to about 95% polyol polynitrate, from about 95 to about 5% nitrocellulose, from about 0 to about 50% inorganic oxidizer, and from about 0 to about 20% fuel.

In some cases, the desensitizing effect of the polyol polynitrate may be excessive. If this is so, there can be incorporated a sensitizing explosive, in an amount to improve sensitivity. Such explosive sensitizers include, for example, trimethylolpropane trinitrate, pentaerythritol tetranitrate, dipentaerythritol hexanitrate, pentolite, tetryl, nitroguanidine, cyclotrimethylene trinitramine (cyclonite, RDX), trinitrotoluene, dinitrotoluene, picric acid, nitropentanone, and nitrostarch. Pentaerythritol tetranitrate is preferred. 1

The proportion of sensitizing explosive can be widely varied, and will depend upon the explosive power and sensitivity desired, and upon the sensitizing explosive. In general, the proportion will be within the range from about 0.5 to about 90% sensitizing explosive, preferably from about 40 to about 75%.

Compositions containing the polyol polynitrate-nitro-v cellulose and a sensitizing explosive are particularly useful in the formation of sheet explosives. In such case, a solution in the nitroparafiin of polyol polynitrate, nitrocellulose, and sensitizing explosive such as pentaerythritol tetranitrate is spread out in a thin film and allowed to set by evaporation of solvent so as to form a gelled sheet. When the composition contains a sufficient proportion of polyolpolynitrate, the gelled composition is sufficiently plastic that it can be Worked with heated rollers, so as to obtain a sheet.

The rate of detonation and sensitivity ofthe sheet will depend upon the percentage of additional sensitizing explosive, such as pentaerythritol tetranitrate, in the final mixture.

In general, the explosive gels in accordance with the invention are obtained by allowing the nitroparaffin solvent to evaporate from the solution under normal atmospheric conditions. The rate of evaporation is slow, but this is beneficial in the formation of a firm gel. However, if desired, the rate of evaporation of the nitroparafiin can be expedited by heating the composition. This can be done by any of a variety of techniques, such as, by placing the composition in an oven, or by extrusion of the composition such as in accordance with the process described in U.S. Patent No. 3,216,307, or by spreading the composition in a film on a moving belt, or on heated rollers, or by dispersing the composition, with agitation, in hot water. In this way, it is possible to prepare a gelled composition which can be set or cast in gelled form, as in an explosive cartridge, or by formulating the composition as pellets, or as powder, or in the form of a sheet, or in the form of a continuous deflagrating or detonating fuse. The following examples in the opinion of the inventors represent preferred embodiments of this invention.

EXAMPLE 1 A solution was prepared composed of 0.5 gram of nitrocellulose (13.2% nitrogen), and 9.5 grams of trimethylolethane trinitrate in 10 grams of nitromethane. This composition wasallowed to set by standing at room temperature in an open vessel, so as to permit the nitromethane to evaporate. After evaporation was complete, a clear and very firm gel having a density of 1.43 g./cc. was formed.

EXAMPLE 2 A gel was prepared by dissolving 1.5 grams of nitrocellulose (13.2% nitrogen), and 8.5 grams of trimethylolethane trinitrate in 30 grams of nitromethane. This gel was allowed to set by standing in an open vessel at room temperature until all of the nitromethane had evaporated. A clear and very firm gel having a density of 1.35 g./cc. was formed.

EXAMPLE 3 A solution was prepared of 2.5 grams of nitrocellulose (12% nitrogen) and 7.5 grams of trimethylolethane trinitrate in 35 grams of nitromethane. This solution was allowed to stand overnight in an open vessel at room temperature. A clear gel having a density of 1.39 g./cc. was formed, that was soft to the touch.

EXAMPLE 4 A solution was prepared containing 2.5 grams of nitrocellulose (13.2% nitrogen) and 7.5 grams of trimethylolethane trinitrate in 70 grams of nitromethane. This solution was allowed to stand overnight in an open vessel, during the course of which the nitromethane evaporated. The gel that was formed was clear, very firm, and had a density of 1.39 g./cc.

EXAMPLE 5 A solution was prepared containing 0.5 gram of nitrocellulose, 9.5 grams of trimethylolethane trinitrate and 5 grams of pentaerythritol tetranitrate in 3 5 grams of nitromethane. This solution was allowed to stand overnight in. an open vessel, whereupon a milky and firm gel having a density of 1.43 g./cc. was obtained.

Each of the above gels was subjected to a series of standard tests to evaluate explosive properties, including ballistic pendulum value, rate of detonation in 2-inch pipe, sensitivity in 2-inch pipe, and crater values.

The sensitivity data showed the safety of handling of the gelled compositions in accordance with the invention. On the other hand, despite the reduced sensitivity, the compositions had excellent explosive power, at a relatively high density, as evidenced by the ballistic pendulum test, rate of detonation, and the crater test results.

EXAMPLE 6 A trimethylolethane trinitrate-nitrocellulose gel was prepared by dissolving 4 parts of nitrocellulose (12.5% N) in parts of nitromethane. To this was added with stirring 16 parts of trimethylolethane trinitrate. The mixture was then spread in a thin layer in a tray, allowing the nitromethane to evaporate, leaving a pliable, clear gel.

A gelatin dynamite was prepared from this gel, having the following formulation:

Percent by weight 7 This composition had a good sensitivity in a 1%" x 8" cartridge, a high density, and an excellent ballistic pendulum value.

EXAMPLE 7 A trimethylolethane trinitrate nitrocellulose gel was prepared by dissolving 25 parts nitrocellulose (13.0% N) in 750 parts 2-nitropropane. 75 parts of trimethylolethane trinitrate was added to this, with stirring.

The mixture was spread into a thin layer on a tray, and the nitropropane allowed to evaporate. The resulting, tough gel was cut into -inch cubes, to form a smokeless powder.

The powder had extremely rapid deflagration imparting a velocity to a rifle ball comparable to standard smokeless powders.

EXAMPLE 8 A trimethylolethane trinitrate nitrocellulose smokeless powder in ball-grain form was prepared as follows: 20 parts of nitrocellulose (13% N) was dissolved in 450 parts of 2-nitropropane in a round-bottom flask with heating and mild stirring at 60 C. When solution was complete, 10 parts of trimethylolethane trinitrate was added to the mixture, 15 parts of gum arabic dissolved in 100 parts of water, was added, and stirring speed increased until spherical globules of the nitropropane solution of nitrocellulose and TMETN had formed, suspended in the gum arabic solution. 20 parts of sodium sulfate dissolved in 100 parts of water was gradually added to the mixture, While increasing the temperature to 90 C. Heating and stirring were continued until all of the 2-nitropropane had evaporated, after which the mixture was gradually cooled to 40 C. The spherical gel particles were filtered out, washed on the filter, and dried. The resulting ball grain powder deflagrated well, and at a velocity comparable to other standard ball-grain powders.

EXAMPLE 9 resulting fuse burned with a constant rate and ignited standard fuse type blasting caps.

EXAMPLE 10 An explosive gel sheet was prepared as follows: 4 parts nitrocellulose was dissolved in 80 parts nitroethane, by warming at 60 C. To this solution was added 10 parts trimethylolethane trinitrate, with stirring, forming a thick solution. Four parts of PETN was added to this solution, with stirring, and the mass was then poured onto a tray, in a layer 7 inch thick. The nitroethane evaporated, leaving a firm gel in sheet form, which had good sensitivity and energy characteristics.

Having regard to the foregoing disclosure, the following is claimed as the inventive and patentable embodiments thereof:

1. A polyol polynitrate-nitrocellulose explosive gel, comprising nitrocellulose and an amount forming a gel with the nitrocellulose of an aliphatic polyol polynitrate in which nitrocellulose is substantially insoluble.

2. A polyol polynitr-ate-nitrocellulose explosive gel in accordance with claim 1, in which the polyol polynitrate is an aliphatic polyol polynitrate having from two to six carbon atoms and not more than one nitro group for each 1.5 carbon atoms, and from two to about five nitro groups per molecule.

3 3. A polyol polynitrate-nitrocellulose explosive gel in accordance with claim 2, in which the polyol polynitrate is trimethylolethane trinitrate.

4. A polyol -polynitrate-nitrocellulose explosive gel in accordance with claim 2 in which the polyol polynitrate is dimethylolethane dinitrate.

5. A polyol polynitrate-nitrocellulose explosive gel in accordance with claim 1, comprising an inorganic oxidizer salt.

6. A polyol polynitrate-nitrocellulose explosive gel in accordance with claim 1, comprising carbonaceous or metallic fuel.

7. A polyol polynitrate-nitrocellulose explosive gel in accordance with claim 6, in which the fuel is a metal.

8. A polyol polynitrate-nitrocellulose explosive gel in accordance with claim 1, comprising another organic sensitizing explosive in an amount to increase the sensitivity of the gel.

9. A polyol polynitrate-nitrocellulose explosive gel in accordance with claim 8 in which the sensitizing explosive is pentaerythritol tetranitrate.

10. A polyol ponynitrate-nitrocellulose explosive gel in accordance with claim 8 in which the sensitizing explosive is a mixture of pentaerythritol tetranitrate and trinitrotoluene.

11. A polyol polynitrate-nitrocellulose explosive gel in accordance with claim 8 in which the sensitizing explosive is trinitrotoluene.

12. A polyol polynitrate-nitrocellulose explosive gel in accordance with claim 8 in which the sensitizing explosive is nitrostarch.

13. A polyol polynitrate-nitrocellulose explosive gel in accordance with claim 8 in which the sensitizing explosive is trimethylolpropane trinitrate.

14. A smokeless powder comprising a particulate polyol polynitrate-nitrocellulose explosive gel in accordance with claim 1.

15. A gelatin dynamite comprising a polyol polynitratenitrocellulose explosive gel in accordance with claim 1, incorporating therein an inorganic oxidizer salt and a carbonaceous or metallic fuel.

16. A semi-gelatin dynamite comprising a polyol polynitrate-nitrocellulose explosive gel in accordance With claim 1, in the form of a solid block.

17. A blasting gelatin comprising a polyol polynitratenitrocellulose gel in accordance with claim 1, in the form of a solid block.

18. A process for forming a polyol polynitrate-nitrocellulose explosive gel, comprising dissolving in a nitroparafiin solvent nitrocellulose and an amount to form a gel with the nitrocellulose of a polyol polynitrate in which nitrocellulose is insoluble, and then volatilizing the nitroparaffin solvent, to recover the gel.

19. A process in accordance with claim 18 in which the nitroparafiin solvent has from one to about six carbon atoms and one nitro group, and a boiling point below about C.

20. A process in accordance with claim 18 in which the nitroparaffin solvent is nitromethane.

21. A process in accordance with claim 18 which comprises volatilizing the nitroparaffin solvent under vacuum.

22. A process in accordance with claim 18 which comprises volatilizing the nitroparafiin solvent at a temperature below about 60 C.

23. A process in accordance with claim 18 which comprises incorporating in the composition, before or after removal of the solvent, an inorganic oxidizer salt.

24. A process in accordance with claim 18 which comprises incorporating in the composition, before removal of the solvent, a carbonaceous or metallic fuel.

25. A process in accordance with claim 18 which comprises incorporating in the composition, before removal of 9 10 the solvent, another organic sensitizing explosive in an References Cited amount to increase the sensitivity of the resulting gel. UNITED STATES PATENTS 26. A process in accordance with claim 25 in which 2,709,130 5/1955 Rinkenbach 149-88 the sensitizing explosive 1s pentaerythritol tetranltrate. 3 307 985 3/1967 Iago 149 96 X 27. A process in accordance with claim 18, which com- 5 3:400:025 9/1968 Hopper et a1 149 94 X prises pelletizing the gel by dispersing the solution in an inert liquid in which it is immiscible, and volatilizing the BENJAMIN PADGETT Pnmary Exammer solvent from the resulting droplets. S. J. LECHERT, JR., Assistant Examiner 28. A process in accordance with claim 18, WhlCh com- 10 Us. Cl XRi prises volatllizing a portion of the solvent to form a VIS- cous mass, and then screening the mass into particulate 64, 751 100 form and volatilizing the remainder of the solvent. 

